Short-circuit current measurements in HBE monolayers reveal GlyH-101 inhibition of basal anion secretion. After amiloride inhibition of ENaC current, a basal anion current was evident. Application of 50 µM GlyH-101 to the apical chamber inhibited the basal current (gray trace) and attenuated the subsequent response to forskolin. In the absence of GlyH-101 (black trace), forskolin stimulated additional anion secretion. Basolateral application of bumetanide inhibited the forskolin-stimulated current in both GlyH-101–treated and untreated epithelia; only the latter were sensitive to basolateral DIDS (see Results). Traces representative of four filters from each condition are shown.